The present invention concerns a device for heating with solar energy, which device contains at least one mirror construction which is mounted on a frame and which can be directed towards the sun, and at least three collectors at equal distance from each other, extending parallel to the mirror construction in order to collect the solar radiation reflected by the mirror construction, whereby the mirror construction contains a number of almost flat mirror strips extending next to one another in the longitudinal direction of the collectors and with their longitudinal direction northward/southward and which are each provided on the frame such that they can rotate around their longitudinal direction, whereas the collectors are stationary in relation to the frame, whereby the mirror strips are situated in an almost horizontal plane with their axes of rotation, whereby the device contains means to rotate the mirror strips and the mirroring surface of the mirror strips such that the solar rays coming in on said surface can be reflected towards the collectors and control means commanding the means to rotate in function of the position of the sun.
U.S. Pat. No. 3,861,379 discloses a device of the above mentioned type except that it contains only one collector All mirror strips are directed to this single collector and are pivoted together for tracking the sun.
When the sun is low, the angle between the incident solar rays and the rays reflected towards the collector will he larger than 90xc2x0 for a number of the mirror strips, what reduces the efficiency.
Devices of the kind described in the first paragraph are disclosed amongst others in FR-A-1,520,370 and U.S. Pat. No. 4,229,229
These known devices contain two or more collectors and underneath each collector a series of mirror strips which may be rotated in function of the position of the sun.
The mirror strips of each series of mirror strips are always directed with their mirroring surface towards a same single collector which is then situated in the middle above the series of mirror strips.
In fact the last mentioned devices may be considered as consisting of two or more of the above mentioned known device as described in U.S. Pat. No. 3,861,379, places one after the other.
The angle between the incident solar rays and the rays reflected towards the collector will be larger than 90xc2x0 for a number of the mirror strips, except when the sun is in its highest position above the mirror construction. The moment at which this angle becomes an acute angle coincides with different positions of the sun for these mirror strips and thus takes place at different points in time.
Mirror strips whose above-mentioned angle is larger than 90xc2x0 make the efficiency of the device decrease.
The aim of the invention is to avoid this drawback.
To this aim, according to the invention, when three adjacent collectors are considered, the mirror strips thereunder are divided into two series, the mirror strips of one series reflecting to the collector situated in the middle while the mirror strips of the other series reflect to the one of the other two collectors situated above the series, the control means commanding the means to rotate in such way that, in the morning, a first series of mirror strips situated between the middle collector and the collector situated to the east thereof reflect towards this latter collector, whereas the second series of mirror strips situated between the middle collector and the collector situated to the west thereof reflect towards the middle collector and that, after the sun has massed its highest point during the day, i.e. in the afternoon, the first series of mirror strips reflect towards the middle collector and the second series of mirror strips reflect towards the collector situated to the west thereof.
In fact, the mirror construction can be regarded as two segmented, semi-parabolic mirrors which extend parallel to one another and whose segments have been flattened have been brought in a horizontal plane.
The first mirror construction can be further extended with one or several additional series of mirror strips and with an extra collector for every series.
The rotation device for rotating the mirror strips can be means to rotate at least a number of the mirror strips, for example all the mirror strips situated between two collectors or all the mirror strips together, simultaneously and to the same extent.
The device may include a wheel, for example a sprocket wheel or a toothed wheel on at least one end of each of the mirror strips, an endless element, for example a chain or toothed belt, working in conjunction with all these wheels, and drive means for driving this element.
The collector preferably contains at least one heat-absorbing pipe and at least one reflector, preferably consisting of two parabolic bent mirrors, directed towards the pine situated in between and which is erected above the pipe like a cap for collecting the solar rays reflected by the mirror construction and for reflecting them to the pipe.
This pipe preferably is a double-walled glass tube whose inner wall is coated with a heat-absorbing material on the outside and with a vacuum between both walls. Through this pipe may extend a metal tube, whereas the space between this metal tube and the pipe may be filled with a heat-transferring material such as steel wool.